Appearing on BBC Radio 4's Today programme this morning Kenneth Clarke, the shadow business secretary, fell into a small hole. He started endearingly by wandering down memory lane saying "in my day", forgetting he is supposed to be still very much in his day. He then endorsed the commission's call for a faster reduction of the deficit, at which point Byrne pounced, claiming Clarke had just committed his party to further cuts.

Sensing he needed to get back on message – territory that he rarely inhabits for long – Clarke said the Conservative goal was to cut the bulk of the structural deficit by the end of the parliament. "Bulk" is a conveniently imprecise word.

The Treasury points out its deficit reduction plan sees the structural, as opposed to cyclical, deficit fall by 2/3 from 9% in 2009-10, to 3.1% in 2014-15. Is a two-thirds cut the bulk of something or not?

I suspect Treasury ministers will try to find out the answer from the shadow chancellor at Treasury oral questions later this afternoon.